The invention is directed to a sewing device with a sewing machine being movable by a robot arm or another moving device and adapted to be led e.g. along the intended seam line.
The common sewing machines (e.g. according to the book of Wilhelm Renters "Die Nahmaschine in Schule und Haus", 1951, publishing company Hermann Kayser, Kaiserslautern) are stationary. They comprise a plate onto which the material to be sewn is placed, as well as a holding-down member which presses the material to be sewn against the plate. The needle stitches into the material to be sewn through a recess in the plate with the upper thread being taken along by the needle. Under the needle plate, there is a substantially drum-shaped shuttle containing a thread bobbin with the lower thread. The shuttle is synchronously driven with the needle movement and it effects a loop formation between the upper thread and the lower thread. Such sewing machines require a transport of the material to be sewn by the sewing machine during sewing.
Further, sewing machines are known which are mounted to a moving device and which are moved along the intended seam line. The moving device can be configured such that the sewing machine can carry out movements in three-dimensional space while the material to be sewn is retained on a support for the material to be sewn.
In sewing machines, the upper thread is pulled off a thread bobbin being capable of receiving a relatively large amount of thread. The lower thread, however, is arranged on a bobbin being arranged in the shuttle and having relatively small dimensions and only being capable of receiving a relatively small thread supply of e.g. a length of 30 m (a length of 70 m at maximum). Therefore, this bobbin has to be changed often. Any change of the lower thread bobbin has to be effected manually by an operator which requires a lot of time. During the whole period of changing the bobbin, the sewing machine is inoperative.